Michael Cohen, President Donald Trump’s former lawyer, has met multiple times with special counsel Robert Mueller’s investigators, including within the past month, according to people familiar with the matter.

As part of the meetings, investigators asked Cohen questions about Trump, including about the president’s business dealings with Russia, one of the people said. Cohen’s lawyer had previously said his client was open to meeting with Mueller but it wasn’t clear the special counsel would want to do so.

Mueller is investigating whether Trump associates colluded with Russia’s efforts to interfere in the 2016 U.S. election. Trump has denied collusion and decried the investigation as a “witch hunt,” and Moscow has denied interfering in the election. Trump has said he would consider a move by Mueller to investigate his business dealings a red line, telling the New York Times last year: “I think that’s a violation.”

Cohen’s decision to cooperate with Mueller’s investigators could escalate pressure on the president and his associates. Cohen has worked with the president for more than a decade and served as Trump’s self-described “fixer” for some of his boss’s thornier projects.